We don’t know yet which brackets will come off, but at least we’re getting a good sense of the different camps in the negotiations – the developed countries like the U.S., major developing nations (India, China, and so on), highly vulnerable countries including small island states, and so on. The latter in particular have drawn much attention due to their extreme exposure to sea level rise and the perception that many larger greenhouse gas emitters aren’t willing to take the tough steps necessary to save them.

But Thomas Lovejoy, a noted environmental scientist and ecologist who spoke with me from Paris Thursday, said he found this common narrative of a divide between major emitters (especially the U.S.) and small islands rather odd, in the following sense.

“People are talking about sea level rise and the fate of small island states as though it has nothing to do with the rest of the world,” said Lovejoy, a professor at George Mason University who has conducted decades of research on the Amazon rainforest, and who is also a senior fellow at the U.N. Foundation. “And we know that it will be disastrous for the eastern United States coastline, and the Gulf Coast.”

“Basically, we should make common cause with the small island states,” Lovejoy says.

Granted, some small islands have their very existence at stake — the highest elevation in the Maldives is 2.4 meters. That’s certainly not true of the U.S. But the point remains that Americans, who are responsible for far more climate-changing emissions than these low-lying places, shouldn’t get the idea that they’re somehow disconnected or insulated from the problem of sea level rise.

In fact, we appear already committed to 5 to 7 feet of it over the long term. For the U.S., that “might flood the current location of the homes of more than 9 million people,” I reported in October. And if the West Antarctic ice sheet is indeed destabilized, as some research suggests, that number would surge much higher.

No wonder that the small island states, in partnership with many African and other developing countries, have pushed for a temperature target of holding global warming to 1.5 degrees C, not the far more widely known 2 degree C target.

“Geologists have known for a really long time that the last time the planet was 2 degrees warmer, the oceans were 4 to 6 meters higher,” says Lovejoy. “And it’s like, do you need to know anything more?”

But the U.S. has not, itself, formally embraced the 1.5 C target (which some doubt, incidentally, is still within reach).

The relatively low level of apparent concern about rising seas in the U.S. is particularly odd when you consider that the problem could be considerably worse here than in other parts of the world.

For instance, if there is major ice loss from West Antarctica (but not from Greenland), then gravitational and other mega-scale geophysical factors mean that U.S. coastlines will get considerably more sea level rise than the global average. This is because the ocean is currently tilted upwards towards Antarctica, drawn to the gigantic ice mass by gravity. But if that mass becomes smaller, the ocean sloshes backwards towards the rest of the world.

Here’s a figure, from the University of Bristol’s Jonathan Bamber, that makes this clear:

Credit: Jonathan Bamber

The gist of the image, as I reported back in January, is that if the world gets 11 feet of sea level rise, the U.S. might actually get closer to 14, according to Bamber’s research.

There is also recent evidence that climate change could be causing a slowing of the Atlantic ocean’s circulation, more technically known as the Atlantic meridional overturning circulation. If this circulation were to stop, or even slow significantly, the result would also be extra sea level rise for the U.S. east coast. As I explained back in March:

Waters to the right or east of the Gulf Stream, in the direction of Europe, are warmer than those on its left or west. Warm water expands and takes up more area than denser cold water, so sea level is also higher to the right side of the current, and lower off our coast.

So if you shut down Atlantic ocean circulation, and lose much of this temperature contrast, the U.S. could get as much as an added meter of sea level rise on its east coast.

Indeed, Michael Mann, a climatologist at Penn State University, told me recently that the U.S. might be in line for a sea level rise “quadruple-whammy.” He sees no less than four reasons why we have to worry about sea level: “baseline global sea level rise (from warming oceans and melting land ice) + slowing gulf stream + gravimetric impact of west Antarctic ice loss + glacial isostatic adjustment,” as he puts it by email.

The latter refers to the fact that, as ice falls into the ocean from Antarctica, the Earth’s crust beneath that ice will rebound upward and push water away. That would push still more water our way.

So Lovejoy’s point seems to be a valid one. Small island nations face the very worst threats from sea level rise, and have little way to defend themselves. We can’t do enough to underscore their unique vulnerability.

But many other nations are also imperiled by sea level rise — including the rich ones that emit a lot of greenhouse gases. They’re hardly insulated or protected. So by helping the small island states, the U.S. would, at the same time, be helping itself.

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